Bipolar Transistor Single Electron Counting via Segmented Junctions
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Solution Overview
Problem
Current semiconductor devices lack the capability to accurately measure small currents or voltages with high precision and efficiency, particularly in detecting single charge carriers, due to limitations in avalanche multiplication and quenching mechanisms.
Innovation Solution
A semiconductor device incorporating a vertical bipolar transistor with a quenching component and an active quenching circuit, configured to operate above the collector-to-base breakdown voltage, enables single electron counting by generating digital pulses from collector current, utilizing a photodiode as a current or voltage source and employing a counter and processing unit to determine the measurement results in digital form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reverse bias is used to increase the width of the depletion region in a p-n junction, then the detection capability for single charge carriers is improved, but the device cannot sustain the high voltage required for avalanche multiplication
Solution Approach 1:
The device is segmented into two distinct p-n junctions: a first p-n junction optimized for detection (operating below breakdown voltage) and a second p-n junction optimized for avalanche multiplication (operating above breakdown voltage). This segmentation allows each junction to operate in its optimal voltage regime, resolving the contradiction between detection capability and voltage sustainability.
Solution Approach 2:
The first p-n junction acts as an intermediary that detects single charge carriers and triggers the avalanche process in the second p-n junction. This intermediary structure enables the system to detect single carriers without requiring the entire device to sustain the high breakdown voltage continuously.
2Stability of the object's composition
If the operating voltage is decreased to the breakdown voltage or below to sustain the device, then the device stability is improved, but the avalanche multiplication effect is lost
Solution Approach 1:
The device separates the detection function (requiring stability, operating below breakdown voltage) from the amplification function (requiring high power, operating above breakdown voltage) into two distinct junctions. This allows each junction to operate in its optimal regime without compromise.
Solution Approach 2:
The first p-n junction continuously operates in a stable detection mode, while the second p-n junction is triggered into avalanche mode only when needed (upon detection of a single charge carrier). This continuous useful action in the detection junction maintains stability while enabling periodic high-power avalanche events.
3Productivity
If a quenching component is added to stop the avalanche current, then the device readiness for subsequent counts is improved, but the device complexity increases
Solution Approach 1:
The quenching function is merged with the existing p-n junction structure by utilizing the inherent properties of the first p-n junction to quench the avalanche in the second junction. The detection junction naturally stops the avalanche process, eliminating the need for separate complex quenching circuitry.
Solution Approach 2:
The first p-n junction serves dual functions: detecting single charge carriers and automatically quenching the avalanche current in the second junction. This self-service mechanism reduces external complexity while maintaining high productivity for subsequent counts.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for precise measurement of small currents, achieving high sensitivity and dynamic range in analog-to-digital conversion, enabling the detection of single electron events with reduced noise and increased readiness for subsequent counts.
Implementation Method 1
the bipolar transistor is configured for operation at a reverse collector-to-base voltage above the collector-to-base breakdown voltage
Implementation Method 2
the current or voltage source comprises a photodiode
Data Source
AI summary
The semiconductor device comprises a bipolar transistor with emitter, base and collector, a current or voltage source electrically connected with the emitter, and a quenching component electrically connected with the collector, the bipolar transistor being configured for operation at a collector-to-base voltage above the breakdown voltage.